1. Field of Invention
This invention relates, in general, to an apparatus for capturing and extracting renewable energy, and in particular, to an apparatus for extracting ocean wave and current energy and converting it into electricity, hydrogen, or other useful form of energy.
2. Description of Prior Art
Various types of wave energy capture concepts have been proposed in the prior art. Many of these have been tested and some operated at sea, but none have resulted in large scale, cost-effective wave energy capture and hence lack commercial viability. The shortfalls of prior concepts consistently fall into several categories; they are point absorbers and capture a small amount of energy, they rely primarily on the rise and fall of the waves and miss the horizontal energy component of the waves and current, they do not effectively account for tidal motion, they place precision generating equipment in the corrosive salt water environment, their complexity drives large installation and operating costs, and they are vulnerable to severe weather. These factors combine to render proposed systems inefficient in the capture of wave energy. The present invention resolves the problematic issues in prior art and represents significant advancements.
Specifically as applied to the prior art, U.S. Pat. No. 3,828,557 discloses a device that captures energy from the pushing action of the waves. This is a point absorber, does not optimally adjust with the tidal shifts, and captures energy only from the incoming action of the wave.
U.S. Pat. No. 4,514,644 discloses a pumping unit driven by a horizontal boom. The boom is connected to a pump that subsequently drives a generator. Energy is lost repositioning the boom, the unit does not adjust for tidal shifts, and the conversion device requires pumped intermediate energy storage.
U.S. Pat. No. 4,560,884 discloses a float attached to an arm on the underneath side of a platform that drives a piston. This design is a point absorber requiring a large number of devices for substantial energy capture, relies primarily on the rise and fall of the waves, does not adjust efficiently to tidal shifts, and requires intermediate energy storage.
U.S. Pat. No. 4,754,157 discloses a cylinder and a rod extending out of the cylinder connected to a float. The action of the wave on the float drives a generator. This approach is a point absorber, limited to energy capture in one relatively small location, and requiring many such devices to be installed to generate substantial energy. The generating equipment is in the salt water, there is no adjustment for tidal shift, and the primary means of energy capture is the rise and fall of the waves.
U.S. Pat. No. 4,931,662 discloses a device consisting of a rigid beam with a float on one end; the motion of the waves drives the beam and pumps a fluid. The float moves in a vertical direction, capturing only the rise and fall of the waves. The design is a point absorber, requiring a large number of similar devices to capture substantial energy, and there is no mechanism to account for tidal shift.
U.S. Pat. No. 5,094,595 discloses a machine embedded on the ocean floor and using multistage axial flow piston compressors to pump a fluid and ultimately drive a generator. This design is a point absorber, places precision equipment under the ocean, requires intermediate pumped storage of energy, and is vulnerable to severe weather.
My own patent, U.S. Pat. No. 5,708,305 also represents another type of point absorber. While the paddles are placed on a horizontal boom, energy is captured at only one point and ocean testing has shown that the disclosed configuration will drive the paddles to float to the very top of the wave and thereby miss most of the available energy. The system requires intermediate pumped storage and a multi-tiered structure that will be costly and vulnerable to severe weather. The means for adjusting for tidal shift reduces the overall efficiency of the system at lower water levels.
U.S. Pat. No. 5,808,368 discloses a float that is attached to pivoting device mounted on a submerged anchor. The float represents a point absorber and is dependent on the vertical action of the waves to actuate the system. The design will miss substantial amounts of available energy and does not appear to optimally adjust for tidal variations.
U.S. Pat. No. 6,756,695 discloses a float with excessive buoyancy that drives a turbine. Here again, this is a point absorber requiring many devices and places a turbine in the saltwater environment. The system depends on the vertical rise and falls of the waves and misses much of the horizontal energy.
Foreign patent Japan Pat. No. 58-91372 discloses a device suspend on a vertical arm that moves back and forth in the water. This is a point absorber, not designed to the shape of the waves, and will require many devices to capture a large amount of energy. Rotation of the arm will cause the device to rise up out of the water and while offering a means to return to the original position, it will miss a substantial amount of energy as the arm elevates.
As demonstrated by the above references, known devices suffer from similar problematic issues. Ocean waves represent a very attractive renewable energy resource; however, the waves present an unpredictable, asynchronous source that has resulted in the limited utility and application of existing concepts. Prior designs were not optimized for the shape of the waves as they pass through the ocean. The present invention has been demonstrated and has been shown to resolve the problematic issues in other concepts, and therefore advances the state-of-the-art well beyond any existing devices.